This invention relates generally to carrier tapes and more particularly, it relates to an improved carrier tape system for transporting electronic components, pharmaceuticals, and the like during production and assembly operations. In addition, there is provided an apparatus for forming the improved carrier tape system which is achieved by making modifications to an existing carrier tape joining device.
As is generally known, carrier tapes are commonly used to transport miniature or subminiature components or products from one station to another in production and assembly operations. Such carrier tapes are typically formed of a base strip of plastic, paper or the like and a cover strip. The base strip is formed with a plurality of cavities or pockets for holding the components and the cover strip is secured to the base strip so as to avoid accidental falling of the components from the cavities. Heretofore, the cover strip was most commonly held in place by an adhesive, heat bond or spaced snap-type fasteners. Typical examples of these types of prior art carrier tapes are disclosed in U.S. Pat. Nos. 3,465,874; 3,650,430; 3,700,019; 3,894,896; 3,910,410; and 4,298,120.
In addition to the above patents, there are various prior art carrier tapes which utilize a continuous mechanical interlock for securing together the base strip and the cover strip. For instance, in application Ser. No. 913,131 filed on Sept. 25, 1986, and entitled "Reuseable Carrier Tape," there is disclosed a carrier tape construction in which the base and cover strips are uniformly and consistently secured to each other. At least one of the strips is provided with an integrally formed, longitudinally extending continuous profile which cooperates with surfaces of the other strip to secure the two strips in a locking engagement. In application Ser. No. 008,293 filed on Jan. 29, 1987, and entitled "Carrier Tape," which is a continuation-in-part of application Ser. No. 913,131, there is disclosed a carrier tape which includes an elongated base strip, an elongated cover strip, and at least one elongated profile strip bonded to one of the other strips, preferably the base strip. The profile strip is provided with a longitudinally extending continuous, integrally formed profile which cooperates with the surfaces of the cover strip to secure the base and cover in a locking engagement. This application Ser. No. 008,293 has now matured into U.S. Pat. No. 4,708,245 on Nov. 24, 1987.
In application Ser. No. 046,259 filed on May 4, 1987, and entitled "Improved Carrier Tape and Cover Applying and Removal Devices For Same," which is a continuation-in-part of application Ser. No. 008,293, there is disclosed an improved carrier tape comprising an elongated base strip and an elongated cover strip both formed of a plastic film material. The base strip is provided with longitudinally spaced cavities for components to be transported therein as well as a series of spaced, longitudinally extending sprocket drive holes for advancing the tape through an associated assembly machine. The cover strip has sidewalls extending downwardly and terminating in inwardly directed barbs or profiles. The spacing between the sidewalls is substantially equal to the width of the base strip. A raised, longitudinally extending hump is provided projecting upwardly from the top surface of the cover strip. When the hump is depressed, the sidewalls of the cover strip move laterally outwardly so as to clear the edges of the base strip and thus permit removal of the cover strip. On the other hand, when the hump is released, the sidewalls return to their relaxed positions securely interlocking with the base strip edges.
Further, there is described in application Ser. No. 046,259 a device for applying the cover strip to the base strip which includes means for applying pressure to the hump of the cover strip and means for guiding the sidewalls of the cover strip around the edges of the base strip. All of the previously mentioned application Ser. Nos. 913,131; 008,293; and 046,259 are assigned to the same assignee as this invention and are hereby incorporated by reference.
In use, the prior art carrier tapes are usually wound around a storage reel for shipping and handling. As a result, there have been encountered heretofore the development of stresses between the base strip and the cover strip as they are wrapped onto the storage reel. This is caused by the tension variations produced by the reel which affects the carrier tape closer at the center of the reel differently than the portions of the carrier tape further away from the center. Consequently, the base and cover strips tend to slip or stretch with respect to one another during the winding process, thereby effecting a premature separation between the base strip and the cover strip at certain portions of the carrier tape and thus rendering possible loss of components. All of the various prior art methods of securing the base strip and the cover strip previously discussed (i.e., either by adhesion or mechanical interlock) suffer from this problem of stresses created during the assembly operation.
Accordingly, it would therefore be desirable to provide an improved carrier tape system in which the base strip and the cover stip are mechanically interengaged so that they are permitted to slide or creep relative to each other when wound around a storage reel. It would be also expedient to provide an apparatus for mechanically interconnecting the base and cover strips of such carrier tape system to each other.